mucous membranen. A membrane lining all body passages that communicate with the exterior, such as the respiratory, genitourinary, and alimentary tracts, and having cells and associated glands that secrete mucus. Also called mucosa.

(my'kəs) Any of the membranes lining the passages of the body, such as the respiratory and digestive tracts, that open to the outside. Cells in the mucous membranes secrete mucus, which lubricates the membranes and protects against infection.